* Surprise fall in Chicago PMI data weighs
* FTSE 100 puts in best ever quarterly performance
* Banks, miners hit by profit taking on last day of quarter
* Energy stocks weak on demand concerns
By Tricia Wright
LONDON, Sept 30 (Reuters) - Britain's top share index closed lower on Wednesday after disappointing Chicago PMI data, with energy stocks, banks and miners among the biggest laggards on the last session of a strong quarter.
The FTSE 100 closed down 25.82 points, or 0.5 percent, at 5,133.90 as investors locked in profits after the index put in its best quarterly performance since it was launched in 1984.
A negative for the market came after a report which showed business activity in the U.S. Midwest failed to return to growth in September as expected, and instead got slammed by a decline in production and new orders.
A powerful rally over the course of the summer has seen British blue chips rise 20.8 percent in the three months to September -- although the index is still 5.2 percent below its level just over a year ago before the collapse of Lehman Brothers.
"With gains like that it's not surprising that there's a little bit of window dressing going on as we finally come down to the wire, and banks and miners have been spectacularly successful during the past quarter," said Jim Wood-Smith, head of research at Williams de Broe.
Energy stocks were the biggest drag on blue chips on demand concerns after weak U.S. consumer confidence data on Tuesday, although crude prices rose above $68 a barrel on the back of U.S. inventory data.
BP, Royal Dutch Shell, BG Group, and Tullow Oil shed 0.7 to 2.3 percent.
UK miners were also under pressure, retreating after a rally earlier in the session, as profit takers moved in on a sector which has surged 26.5 percent this past quarter.
Anglo American, BHP Billiton, Fresnillo and Vedanta Resources dropped between 0.4 and 2.5 percent.
It was a similar story with banks which were broadly lower, falling back after gains earlier on Wednesday which had been spurred as recent cash calls from peers reassured investors about the path of recovery.
Heavyweight HSBC shed 1.4 percent, while Lloyds Banking Group retreated 1.1 percent.
Royal Bank of Scotland, Standard Chartered, and Barclays, however, rose 0.2 to 1.8 percent.
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Marks & Spencer shed 3.4 percent after a second-quarter trading update prompted profit-taking.
Analysts said better-than-expected sales and profit margins were factored into a recent rally in M&S shares, while a downgrade in its cost guidance was not.
Clothing retail peer Next fell 3.1 percent.
Thomas Cook lost 3.5 percent after the tour operator's fourth-quarter trading update failed to impress.
Reed Elsevier shed 1.2 percent with Goldman Sachs said to be placing 22 million shares in the publishing group on behalf of an institutional investor, according to traders.
On the upside, life insurers saw strong demand with the sector boosted by a resurgence of M&A speculation.
Legal and General was among the top blue-chip risers, up 6.1 percent following recent reports it could be a target for a number of companies, and supported too as Deutsche Bank raised its rating on the firm to "hold" from "sell".
RSA Insurance, Aviva, Standard Life, and Prudential also rallied, up 0.5 to 3.9 percent, underpinned by Deutsche Bank's upbeat note on life insurers.
Among other financials, Man Group grabbed the top spot on the FTSE 100 leader board, adding 7.5 percent after the hedge fund manager said currency movements and slowing outflows lifted funds under management to an estimated $43.8 billion at end-September, at the top end of forecasts. (Editing by David Cowell)